There are various standards around the world which are used as the standards for connecting TVs, video decks, and other equipment together. One of these is the SCART (Syndicat des Constructeurs d'Appareils Radiorecepteurs et Televiseurs) standard which enables video signals and audio signals to be carried over a single cable between devices. This SCART standard is being adopted to a large number of apparatuses in Europe etc.
Further, set top boxes which have SCART connectors based on the SCART standard and enable TVs, video decks, etc. to be connected all together are also being utilized in large numbers. In such set top boxes, it is possible to convert the audio signals and video signals from each of the equipments to for example output signals etc. for the TVs and to output them to the TVs etc. Further, set top boxes may be connected to cable TV systems, TV antennas, audio equipment, etc. in addition to being connected to equipment using SCART connectors.
In this SCART standard, to enable the screen size of the video signal to be discerned, a direct current voltage which shows the screen size is used as a blanking signal and transferred by terminals (pins) of the SCART connectors. The direct current voltage which shows the screen size is, for example, a 12V or 6V or 0V voltage level.
For this reason, the set top box has a video blanking signal processing circuit which is provided with a direct current voltage output circuit for outputting these direct current voltages. As general direct current voltage output circuits, for example, there are the circuits which are described in the following Patent Documents 1 to 4.
These direct current voltage output circuits are configured to be provided with MOS transistors and other switching device, resistors, etc. Further, the direct current voltage output circuits are configured so that control signals which are output from control circuits etc. at the inside of the set top boxes are used to switch the conduction states of the MOS transistors and thereby output the desired voltage levels of direct current voltages.